The invention relates to utility meter transmitter assemblies for use in RF metering networks.
In recent years, the desire to automate collection and billing of utility consumption data has led to the introduction of various metering networks, including RF networks in which data is collected from fixed transmitting stations which are connected to one or meters for metering gas, electricity or water usage.
As further disclosed in Cerny et al., a radio frequency (RF) transmitter may transmit signals representing meter consumption data to a mobile collection unit which may be carried in a vehicle or which may be carried by a person. Radio frequency transmitters may also be used to transmit signals from stationary transmitting units to stationary data collection units at specific locations. In this type of system, it has become necessary to provide transmitters and antennae with greater power and greater range than in prior art equipment.
Examples of prior art transmitters and antennae are disclosed in Cerny et al., U.S. Pat. No. 5,298,894, and Bloss et al., U.S. Pat. No. 5,877,703. Cerny et al. discloses that the antenna assembly can be separate from, or integrated with, the transmitter assembly.
It is also desirable to make the antenna assemblies compact in size, low in cost of manufacture, durable and easy to install and service.
The invention relates to an antenna assembly for RF utility metering equipment, and particularly to an antenna assembly including a capacitance which can be tuned to provide a selected operating frequency. The invention also relates to a method of making such an assembly.
More specifically, the present invention is an antenna assembly for RF communication of signals representing utility meter data. The antenna assembly comprises a first conductor forming at least a portion of an antenna radiating element, a second conductor, and a dielectric disposed between the first conductor and the second conductor, such that the first conductor, the second conductor and the dielectric form a capacitor. The antenna assembly further comprises an inductance in cascade with the capacitor to provide a selected L-C circuit impedance in relation to the antenna radiating element. The second conductor is disposed opposite to the first conductor and at least one of the first and second conductors is movable from a first to a second position to adjust the capacitance of the L-C circuit to a selected frequency of operation.
It is one object of the invention to provide the ability to tune the frequency of the antenna for increased accuracy and decreased manufacturing costs as compared to prior art devices.
It is another object of the invention to provide an antenna assembly in which each of the first and second conductors includes a plurality of apertures alternating with portions of conductive material, and wherein a misalignment of the apertures in the respective conductors adjusts the capacitance to tune the L-C circuit
It is yet another object of the invention to provide apertures in the first and second conductors that are formed as 45-degree sectors alternated with 45-degree sectors of conductive material.
It is still another object of the invention to provide apertures in the first and second conductors which are arranged symmetrically to provide a symmetrical radiation pattern.
A still further object of the invention to provide a variable capacitance to tune the antenna assembly to an operating frequency of substantially 915 MHz.
Yet a still further object of the invention is to provide a variable capacitance to tune the antenna assembly to a frequency between 820 MHz and 1.2 GHz.
Other objects and advantages of the invention, besides those discussed above, will be apparent to those of ordinary skill in the art from the description of the preferred embodiments which follow. In the description, reference is made to the accompanying drawings, which form a part hereof, and which illustrate examples of the invention. Such examples, however, are not exhaustive of the various embodiments of the invention, and therefore, reference is made to the claims which follow the description for determining the scope of the invention.